Method for the cascaded coding and decoding of audio data

Abstract

In a method for the cascaded coding and decoding of audio data the spectral components of the short-time spectrum associated with a data block are formed for each data block with a certain number of time input data, the coded signal is formed, by quantization and coding, on the basis of the spectral components for this data block and using a psycho-acoustic model to determine the bit distribution for the spectral components, whereupon time output data are obtained by decoding at the end of each codec stage. To prevent a deterioration in the sound quality in codec cascades with a plurality of stages, an identification code is added to the coded signal at an initial stage to mark the start of the data block; furthermore, the subsequent codec stages divide the data blocks to be coded on the basis of this identification code.

What is claimed is: 
     
       1. A method for cascaded coding and decoding of audio data comprising the steps of: coding audio data, in each of a plurality of cascaded coding-decoding (codec) stages, so that for a block of audio data with a certain number of time input data, the spectral components of the short-time spectrum associated with this block are formed and so that a coded signal is formed on the basis of the spectral components of the block and a psycho-acoustic model; and   decoding the coded block of audio data, in each of a plurality of cascaded codec stages, so that the coded signal is decoded to produce time output data;   wherein at the coding step in one of the codec stages the time input data are processed such that the coded block of audio data includes an identification code marking the start of the coded block of audio data, the identification code not being removed by the decoding step of this codec stage, and at the coding step in at least one of the subsequent codec stages in the cascade, the division of the input data into blocks of audio data to be coded is performed on the basis of the identification code.   
     
     
       2. The method of claim 1, wherein the identification code indicates its coded block's first sampling value. 
     
     
       3. The method of claim 2, wherein at least in mutually homogeneous codec stages within a codec chain, synchronous block formation with the same block size and with the same location of the division of the data in blocks is performed on the basis of the identification code. 
     
     
       4. The method of claim 1, wherein audio data is coded according to the standard AES-3. 
     
     
       5. The method of claim 1, wherein audio data is coded according to the standard IEC958. 
     
     
       6. The method of claim 4, wherein for blocks of audio data whose size is an integral multiple of the AES-3 block size, the blocks are arranged within the AES-3 raster and the identification code consists of a special preamble ("Z2"). 
     
     
       7. The method of claim 4 wherein the identification code indicates its coded block's first sampling value, and, further, wherein for blocks of audio data whose size is not an integral multiple of the AES-3 block size, the identification code indicating the first sampling value of the coded block is located in a "user-data" bit of the block concerned.